Diphosphites having an open and a closed 2,4-methylated outer unit

ABSTRACT

Diphosphites having an open and a closed 2,4-methylated outer unit and use thereof in hydroformylation.

The invention relates to diphosphites having an open and a closed2,4-methylated outer unit and use thereof in hydroformylation.

Phosphorus-containing compounds play a crucial role as ligands in amultitude of reactions, e.g. in hydrogenation, in hydrocyanation andalso in hydroformylation.

The reactions between olefin compounds, carbon monoxide and hydrogen inthe presence of a catalyst to give the aldehydes with one carbon atommore are known as hydroformylation or the oxo process. In thesereactions, compounds of the transition metals of group VIII of thePeriodic Table of the Elements are frequently employed as catalysts.Known ligands are, for example, compounds from the phosphine, phosphiteand phosphonite classes, each containing trivalent phosphorus Pul. Agood overview of the situation on the hydroformylation of olefins can befound in R. Franke, D. Selent, A. Bömer, “Applied Hydroformylation”,Chem. Rev., 2012, DOI:10.1021/cr3001803.

The following compound is shown in EP 0213639 A2 on page 98 in example10:

The compound (2) is used here as ligand in the hydroformylation of1-butene.

The technical object of the invention is to provide novel ligands thatexhibit increased n/iso selectivity in the hydroformylation of olefinscompared with the ligand known from the prior art.

The object is achieved by a compound according to claim 1,

Compound of the structure (1):

where R¹, R² are selected from: -H, -(C₁-C₁₂)-alkyl, -0-(C₁-C₁₂)-alkyl.

In one embodiment, R¹, R² are selected from: -H, -(C₁-C₁₂)-alkyl.

In one embodiment, R¹, R² are -(C₁-C₁₂)-alkyl,

In one embodiment, R¹, R² are the same radical.

In one embodiment, the compound has the structure (1):

As well as the compound per se, the use thereof for catalysis of ahydroformylation reaction is also claimed.

Use of a compound described above in a ligand-metal complex forcatalysis of a hydroformylation reaction.

Additionally claimed is a process in which the above-described compoundis used as a ligand.

Process comprising the process steps of:

-   a) initially charging an olefin,-   b) adding an above-described compound and a substance containing a    metal selected from: Rh, Ru, Co, Ir,-   c) supplying H₂ and CO,-   d) heating the reaction mixture from steps a) to c), with conversion    of the olefin to an aldehyde.

In a preferred embodiment, the metal is Rh.

The ligands can also be used in excess here and it is not automaticallythe case that each ligand is present in bound form as a ligand-metalcomplex; it may instead be present in the reaction mixture as the freeligand.

The reaction is carried out under customary conditions.

Preference is given to a temperature of 80° C. to 160° C. and a pressureof 10 to 60 bar. Particular preference is given to a temperature of 100°C. to 140° C. and a pressure of 20 to 50 bar,

The reactants for the hydroformylation in the process of the inventionare olefins or mixtures of olefins, especially monoolefins having 2 to24, preferably 3 to 16 and more preferably 3 to 12 carbon atoms, andhaving terminal or internal C-C double bonds, for example 1-propene,1-butene, 2-butene, 1- or 2-pentene, 2-methyl-1-butene,2-methyl-2-butene, 3-methyl-1-butene, 1-, 2- or 3-hexene, the C₆ olefinmixture obtained in the dimerization of propene (dipropene), heptenes,2- or 3-methyl-1-hexenes, octenes, 2-methylheptenes, 3-methylheptenes,5-methyl-2-heptene, 6-methyl-2-heptene, 2-ethyl-1-hexene, the Ca olefinmixture obtained in the dimerization of butenes (di-n-butene,diisobutene), nonenes, 2- or 3-methyloctenes, the C₉ olefin mixtureobtained in the trimerization of propene (tripropene), decenes,2-ethyl-1-octene, dodecenes, the C₁₂ olefin mixture obtained in thetetramerization of propene or the trimerization of butenes (tetrapropeneor tributene), tetradecenes, hexadecenes, the C₁₆ olefin mixtureobtained in the tetramerization of butenes (tetrabutene), and olefinmixtures having different numbers of carbon atoms (preferably 2 to 4)produced by cooligomerization of olefins.

The process of the invention using the ligands of the invention can beused for the hydroformylation of α-olefins. terminally branched,internal and internally branched olefins.

The invention shall be illustrated in detail hereinbelow with referenceto exemplary embodiments.

WORK PROCEDURES

General analysis

All the preparations that follow were carried out under inert gas usingstandard Schlenk techniques. The solvents were dried before use oversuitable drying agents.

The products were characterized by NMR spectroscopy. Chemical shifts (δ)are reported in ppm. The ³¹P NMR signals were referenced as follows:SR³¹P=SR¹H * (BF³¹P/BF¹H)=SR¹H * 0.4048.

Synthesis

Synthesis (1a)

In a 500 ml Schienk flask with baffles, 10.7 g of2,2′-bis(3,5-dimethyl)phenol (vacuum oil pump dried) were initiallycharged dissolved in 100 of toluene and heated to 40° C. In a glovebox,15.5 g of chlorophosphite were weighed out into a 250 ml Schlenk flaskand evacuated. The chlorophosphite was dissolved with stirring in 150 mlof toluene and 5.6 ml of Et₃N were added. Thechlorophosphite-Et₃N-toluene solution was added slowly over 4 hours tothe initially charged phenol solution at 40° C. After stirringovernight, a further 2.8 mL of Et₃N were added. After 18 hours, 100 mLof degassed acetonitrile were added to the solid with stirring. Themixture was stirred overnight at room temperature, In the morning, themixture was cooled to 0° C. and stirred at this temperature for 2 hours.The mixture was passed through a frit and then washed with a littledegassed cold acetonitrile. The solid on the frit was dried and placedin the glovebox. Purity: 95%, yield 74%.

Synthesis (1b)

50 ml of toluene and 2.75 ml (0.062 mol) of phosphorus trichloride wereadded to a secured 250 ml Schlenk flask after flushing with argon, Inthe glovebox, 6 g (0.02 mol) of (1a) are weighed into a further 250 mlSchlenk flask. After evacuation, 50 mL of toluene and 4.25 mL (0.061mol) of triethylamine are added under argon. After dissolution iscomplete, the solution of (la) is slowly added dropwise to thephosphorus trichloride/toluene solution. The solution was then stirredat 80° C. for 2 hours, then cooled to room temperature and stirredovernight at room temperature. For work-up the next morning, thesuspension is filtered off through a G3 frit, The hydrochloride filteredoff here is discarded. The resulting mother liquor is concentrated todryness at 45° C. by means of a vacuum oil pump.

Yield: 90%, purity 94.5%.

Synthesis (1)

In a glovebox, 7.89 g (0.011 mol) of diorganophosphite dichlorophosphite(1b) were weighed out into a secured 250 ml Schlenk flask, thenevacuated and dissolved in 80 mL of dried toluene. 2.64 ml (2.69 g=0.022 mol) of 2,4-dimethylphenol were filled into a second secured 250ml Schlenk flask by means of an argon-flushed syringe. Then, withstirring, 60 ml of dried toluene and 6.6 ml =4.8 g (0.047 mol) ofdegassed triethylamine were added and dissolved with stirring. To thephenol-triethylamine solution was then added the previously preparedchlorophosphite solution in one go. The reaction mixture was thenimmediately heated to 80° C. and vigorously stirred overnight at thisreaction temperature. For the workup, the resulting amine hydrochloridewas removed by frit at room temperature. To improve the ability of theamine hydrochloride to be filtered off, the stirrer was switched offbeforehand and the reaction mixture allowed to stand for 1.5 hours. Theresulting filtrate was concentrated to dryness and further dried at roomtemperature for 18 hours by means of a vacuum oil pump, The residue wasthen stirred with 100 ml of degassed acetonitrile, which did notdissolve, after which the solvent was again removed. 100 ml of degassedn-heptane were added to the resulting solid. In this case, the majorityof the solid dissolved in the heptane. The cloudy solution was passedthrough a frit. The clear filtrate was concentrated to dryness. Purity76.6%. In order to achieve higher purity. TLC with various eluents werecarried out. The best eluent proved to be the mixture n-heptanelethylacetate 96:4. The product was dissolved in 15 ml of n-heptane and theliquid loaded onto an automated column system. For this purpose, a 120 gsilica gel column was used. With the aid of the Rf values ascertained, agradient was determined by automation. Purity 95%, yield: 30%,

Synthesis () (comparative ligand)

In a glovebox, 9 g (0.01 mol) of diorganophosphite dichlorophosphitewere weighed into a secured 250 mL Schlenk flask, then evacuated anddissolved in 75 mL of dried toluene. In a second secured 250 mL Schlenkflask, 2.2 g (2.1 mL 0,02 mol) of 2-methylphenol were weighed out anddried at room temperature for 12 hours by means of an oil vacuum pump.50 mL of dried toluene and 3 mL=2.2 g (0.022 mol) of degassedtriethylamine were added with stirring and dissolved. Thedichlorophosphite was added at room temperature to thephenol-triethylamine solution over 1.5 hours. The reaction mixture wasstirred at room temperature for 2 hours and then heated to 80° C. Thereaction mixture was stirred at this temperature for 15 hours and then 3times 1.5 mL (0.011 mol) of triethylamine were metered in and left tostir for a further 15 hours. The ammonium hydrochloride was removed byfrit, washed with 1 x 10 mL of dried toluene and concentrated todryness. The solid was dried at room temperature for 15 hours andstirred with 40 mL of degassed acetonitrile. The precipitated whitesolid was removed by frit, the Schlenk flask was post-rinsed with 2times 10 mL of ACN and after drying introduced into a glove box. Yield90%, purity: 95%.

Catalysis experiments The hydroformylation was carried out in a 16 mlautoclave from HEL Group, Hertfordshire, United Kingdom, equipped with apressure-retaining valve, gas flowmeter and sparging stirrer. Then-octene used as substrate (Oxeno GmbH, mixture of octene isomers of1-octene: 3%; cis+rans-2-octene: 49%; cis+trans-3-octene: 29%;cis+trans-4-octene: 16%; structurally isomeric octenes: 3%) was heatedunder reflux for several hours over sodium and distilled under argon.

The reaction solutions for the experiments were prepared beforehandunder an argon atmosphere. For this, 0.0021 g of Rh(acac)(CO)₂ and thecorresponding amount of phosphite compound were weighed out and filledwith 8.0 ml of toluene. The mass of toluene introduced in each case wasdetermined for the GC analysis. 1.80 g of n-octene (16 mmol) was thenadded. The prepared solutions were then introduced into the autoclave,which was flushed three times with argon and three times with syngas(Linde; H₂ (99.999%): CO (99.997%) =1:1). The autoclave was then heatedto the desired temperature at an overall pressure of 10 bar withstirring (900 rpm). On reaching the reaction temperature, the syngaspressure was increased to 20 bar and the reaction carried out atconstant pressure for 4 h. At the end of the reaction time, theautoclave was cooled to room, temperature, depressurized while stirringand flushed with argon. 0.5 ml of each reaction mixture was removed atthe end of the reaction, diluted with 4 ml of pentane and analysed bygas chromatography: HP 5890 Series II plus, PONA, 50 m x 0.2 mm x 0.5μm. Residual olefin and aldehyde were quantitatively determined againstthe solvent toluene as internal standard.

Results of the catalysis experiments

Reaction conditions:

[Rh]: 120 ppm, L:Rh=1:2, p: 20 bar, T: 120° C.; t: 4 h

TABLE 1 Hydroformylation of n-octenes Ligand n/iso selectivity in % 1*77 2 56 *inventive compound

Definition of selectivity:

In the hydroformylation there is n/iso selectivity, which is the ratioof linear aldehyde (=n) to branched aldehyde (=iso). The selectivityhere in respect of the n-aldehyde signifies that this amount of linearproduct was formed. The remaining percentages then correspond to thebranched isomer. Thus, at a regioselectivity of 50%, n-aldehyde andiso-aldehyde are formed in equal proportions.

The compound of the invention (1) achieved an increase in n/isoselectivity compared with the comparative ligand (2).

The experiments carried out demonstrate that the stated object isachieved by the compound of the invention.

1. Compound of the structure (I):

where R¹, R² are selected from: -H, -0-(C₁-C₁₂)-alkyl.
 2. Compoundaccording to claim 1, where R¹. R² are selected from: -H,-(C₁-C₁₂)-alkyl.
 3. Compound according to claim 1, where R¹, R² are-(C₁-C₁₂)-alkyl.
 4. Compound according to claim 1, where R¹, R² are thesame radical.
 5. Compound according to claim 1, where the compound hasthe structure (1):


6. Use of a compound according to claim 1, in a ligand-metal complex forcatalysis of a hydroformylation reaction.
 7. Process comprising theprocess steps of: a) initially charging an olefin, b) adding a compoundaccording to claim 1 and a substance containing a metal selected from:Rh, Ru. Co, Ir, c) supplying H₂ and CO, d) heating the reaction mixturefrom steps a) to c), with conversion of the olefin to an aldehyde.